What is a Fish? Fish are water dwelling, coldblooded creatures in the animal kingdom. Freshwater fish live in

rivers, lakes, streams, ponds, and swamps. They do not live in saltwater. Three characteristics

define a fish:

1. All fish have ______, which allow a fish to maneuver through the water.

2. All fish have ______, which they use to obtain oxygen from the water.

3. All fish are _______________; they have a backbone.

Do all fish have scales? The answer is no.

Some fish, like the catfish, do not have scales. They have skin.

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Answers: 1. fins 2. gills 3. vertebrates

Exterior Parts of a Fish:

4. Caudal Fin

6. Lateral Line

8. Pectoral Fin 5. Anal Fin

3. Dorsal Fin 2. Dorsal Spines

7. Pelvic Fin

1. A fish’s head contains two eyes, two holes that resemble nostrils, 6. The lateral line is covered in sensory nerves that allow a fish to “feel”

and one mouth. vibrations in the water. These “nerves” are located under the scales or skin.

2. Dorsal spines are part of the dorsal fin. 7. The pelvic fins on each side of the fish act like brakes when a fish needs to

3. The dorsal fin is the top fin, which keeps a fish upright in the water. slow down.

The dorsal fin is sometimes separated into two fins on a fish’s back. 8. The pectoral fins on each side of a fish allow a fish to move up, down,

4. The tail fin is called the caudal fin. This fin propels a fish through the water. forward, and backward in the water.

5. The anal fin, like the dorsal fin, also keeps a fish steady in the water. 9. The operculum covers the gills.

1. Head

9. Operculum

Interior Parts of a Fish:

1. Fish, like all vertebrates, have a skeleton for support, which includes the

spine (backbone).

2. This “gas bladder” (or swim bladder) acts like a balloon. If it fills with air,

the fish will rise in the water. If air is released, the fish will sink.

3. The heart pumps blood throughout the body, including to and from the

gills.

4. Gills allow fish to take oxygen from the water.

5. Muscles are connected to the skeleton and allow the fish to move.

6. Eggs are found in female fish. Fish spawn (release their eggs) in the spring.

7. The otolith is a small bone in the fish’s head. You will learn more about this

later!

8. Like humans, fish also have a brain.

9. The olfactory bulb receives information about smells and sends it to the

brain. Remember! Fish have small holes that look like nostrils. Sensory

pads located here allow fish to identify smells!

10. The olfactory nerve sends messages to the brain from the olfactory bulb.

11. The esophagus moves food to the stomach.

12. The stomach starts food digestion; the stomach is connected to the

intestines where more digestion takes place.

13. The intestines lead to the anus where solid wastes are removed from the

body.

14. The anus is the wastes removal site.

15. The urinary bladder collects liquid wastes from the body.

Use the information below to find out more!

1.

2.

3. 4.

5.

6.

7.

8.

9.

10.

11. 12.

13. 14. 15.

How Do Fish Breathe?

Water with oxygen passes through the mouth and over the gills, which are basically red tissue filled with blood vessels.

These blood vessels are located very close to the tissue surface. Oxygen passes through the vessels and into the fish’s

blood stream. From there the heart pumps oxygen rich blood throughout the body and takes blood low in oxygen back to

the gills.

This gas exchange also takes place in human through the alveoli in the lungs. However, humans cannot take oxygen from

water, only air. Fish, on the other hand, cannot take oxygen from the air, only water.

Obviously, fish cannot live out of water. They do not have lungs like humans.

Gills allow fish to take oxygen from the water. So, how do gills work?

?

How does oxygen get into the water? Plants living in or under the water are known as aquatic plants.

Oxygen is released by these plants into the water through the process of photosynthesis. Oxygen can also

dissolve into the water from the atmosphere above.

Oxygen rich

blood leaving

gills

Oxygen poor

blood traveling

to gills

How Do Fish Swim?

Fins come in all sizes and shapes. For example, fish can have

different types of tail fins. The most common are the rounded tail

and the forked tail.

1. The round tail is good for fast swimming, but not for very long.

2. The forked tail allows for faster swimming and for longer times.

3. Some fish tails are shaped between a rounded and forked tail.

4. Other fish have tails shaped like the sturgeon. A sturgeon’s tail is

larger on top than bottom. This is not good for fast swimming, but

it allows the fish to easily swim or “hover” along the bottom of a

lake or river.

Mouths:

Subterminal mouths are located under the head and

usually are “tubed” or “sucker-like” in appearance. This

mouth allows fish to feed on the bottom of a lake or

river.

Examples of freshwater fish with subterminal mouths

are sturgeon, river carpsucker, and smallmouth buffalo.

Terminal mouths are good for snapping and grabbing

prey. Fish, like the gar species, have terminal mouths.

Upturned mouths are just as they are described. These

mouths are turned upwards. Fish with this mouth

usually chase after their food with mouth open to

“gulp” in their prey.

Examples of fish with upturned mouths are largemouth

bass and crappie.

Some fish have jawless mouths like the parasitic

lamprey. These fish have a circular mouth lined with

rows of teeth. They use these teeth to attach to host

fish and suck fluids from them.

What Do Fish Eat?

Carnivores – Feed on meat (smaller fish or large invertebrates)

Herbivores – Feed mainly on plants

Omnivores – Feed on both plants and animals

Planktivores – Feed primarily on plankton, microscopic plants and animals in the water

Detritivores – Feed on decaying matter that remains on the floor of a water body

Colors and Patterns: Fish are different, sizes, shapes, and colors. Some fish

like the spotted gar are covered in a pattern that

allows for good camouflage when hiding from

predators or when “lying in wait” for prey.

Did you know?

Different fish have different types

of scales. Gar are covered in very

hard scales that act like armor.

These hard, thick scales are called

“ganoid” scales.

?

Body Sizes and Shapes:

Spear shaped

Streamlined

Small

Flattened

Pan shaped

Eel shaped

Large

Shovel-nosed

How Do You Determine the Age of a Fish?

Slime Layer:

All fish with a bony skeleton have small, round bones in their head known as “ear stones” or “otoliths.” As fish

grow, new layers are added to this bone. Fish growth slows in the colder parts of the year, so growth rings

appear very close together to form one dark ring every year. Biologist take these bones and count the rings

like a tree.

Fish scales also form these rings in the same way, but remember, not all fish have scales!

3. 2. 1.

Fish have a layer of mucous slime covering them. This slime protects the fish from parasites and bacteria,

keeping the fish healthy.

Fish Development:

Fish hatch from eggs. They develop and change as they grow.

In the wild, fish lay eggs in depressions on the bottom of a water body or attach them to

underwater plants.

Fish can lay anywhere from a few hundred to a few thousand eggs!

Some animals have one or two young, and take care of those young until they can survive on

their own. Other animals, like fish, have many young but do not provide long-term care. As soon

as young fish are feeding and swimming on their own, the parents no longer care for them.

At the North Mississippi Fish Hatchery, fish eggs are collected and kept inside the hatchery.

Newly hatched fish are called fry and are very small.

The fry grow larger in hatchery ponds, developing their digestive system and feeding on

plankton. These larger fish are called fingerlings because they are the size of your finger. These

fingerlings are released into the lakes where they will grow into adult fish.

2. ____________________ 3. ______________________

4. ________________________

1. __________________

Answers: 1. egg 2. fry 3. fingerling 4. adult

Label the Fish Stages Below:

Know the Answer?

See if you can match the right answer!

1. Some fish are small; others are _______.

2. Protective covering on scales/skin _______.

3. Some fish have patterns for ________.

4. Fish that feed on plants _______.

5. Acts like a balloon, allowing a fish to rise in the

water _______.

A. Camouflage

B. Large

C. Herbivores

D. Slime

E. Gas Bladder

Answers: 1. B 2. D 3. A 4. C 5. E

Test Your Knowledge!

Do your best to solve the crossword puzzle below. (Hint: All the answers are in this workbook!)

Down:

1. Fish that feed on plankton 3. A parasitic fish 4. _____ allows fish to take oxygen from the water. 8. Fish hatch from _____.

Across:

2. Another name for the tail fin is the _____ fin. 5. Plants release oxygen through the process of _____. 6. Hard, armor-like scales. 7. A “sucker-like” mouth 9. All fish are _____; they have a skeleton. 10. Fish come in all shapes and _____.

For the Record:

The next time you are fishing, make notes about the fish you catch. (Size, shape, color, etc.)

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Visit www.MDWFP.com to download a copy of the Fish Identification Guide and identify your

fish!

Learn more about freshwater fishing in

Mississippi at www.mdwfp.com.